* Astronomy

Blobrana · L

RE: eta Carinae

Blobrana · L

The star Eta Carinae, which at times brightens like a supernova, also dims every 5.5 years, has begun the process earlier than expected.

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Blobrana · L

VLT images two nebulae in Carina

ESO PR Photo 17a/08
The Homunculus (NACO/VLT)
[Preview - JPEG: 400 x 458 pix - 67k]
[Normal - JPEG: 1001 x 1147 pix - 827k]

This new image of the luminous blue variable Eta Carinae was taken with the NACO near-infrared adaptive optics instrument on ESO's Very Large Telescope, yielding an incredible amount of detail. The images clearly shows a bipolar structure as well as the jets coming out from the central star.
The image was obtained by the Paranal Science team and processed by Yuri Beletsky (ESO) and Hännes Heyer (ESO). It is based on data obtained through broad (J, H, and K; 90 second exposure time per filters) and narrow-bands (1.64, 2.12, and 2.17 microns; probing iron, molecular and atomic hydrogen, respectively; 4 min per filter).

ESO PR Photo 17b/08
NGC 3576
[Preview - JPEG: 481 x 481 pix - 105k]
[Normal - JPEG: 1039 x 1250 pix - 1.2M]

Located 9 000 light-years away, NGC 3576 is a gigantic region of glowing gas about 100 light-years across, where stars are currently forming. The intense radiation and winds from the massive stars are shredding the clouds from which they form, creating dramatic scenery. The black area in the right middle part of the image is dark because of the presence of very dense, opaque clouds of gas and dust.
The data used to make this colour-composite images were taken with ISAAC on the VLT, in the framework of observing proposal 079.C-0203(A). The image processing was done by Yuri Beletsky (ESO) and Hännes Heyer (ESO). It is based on data taken through 4 different narrow-band filters centred around 1.21, 1.71, 2.09 and 3.28 microns.

-- Edited by Blobrana at 17:13, 2008-08-07

Blobrana · L

The star Eta Carinae is estimated to be 100 times heftier than the sun and may also turn out to be one of the shortest-lived.

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Blobrana · L

For the first time, astronomers have pinpointed the spot where the intense winds of two massive stars in a binary system violently collide and detected the production of high-energy X-rays there.
The monstrously large Eta Carinae binary contains between 100 and 150 times the mass of the sun and glows more brightly than four million suns together. The so-called hypergiant contains two massive stars, the second of which was not discovered until 2005.
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Blobrana · L

Title: The Early Spectra of Eta Carinae 1892 to 1941 and the Onset of Its High Excitation Emission Spectrum
Authors: Roberta M. Humphreys, Kris Davidson, Michael Koppleman

The observed behaviour of eta Car from 1860 to 1940 has not been considered in most recent accounts, nor has it been explained in any quantitative model. We have used modern digital processing techniques to examine Harvard objective-prism spectra made from 1892 to 1941. Relatively high-excitation He I 4471 and [Fe III] 4658 emission, conspicuous today, were weak and perhaps absent throughout those years. Feast et al. noted this qualitative fact for other pre-1920 spectra, but we quantify it and extend it to a time only three years before Gaviola's first observations of the high-excitation features. Evidently the supply of helium-ionising photons(lambda < 504A) grew rapidly between 1941 and 1944. The apparent scarcity of such far-UV radiation before 1944 is difficult to explain in models that employ a hot massive secondary star,} because no feasible dense wind or obscuration by dust would have hidden the photoionisation caused by the proposed companion during most of its orbital period. We also discuss the qualitative near-constancy of the spectrum from 1900 to 1940, and eta Car's photometric and spectroscopic transition between 1940 and 1953.

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Blobrana · L

An explosive star within our galaxy is showing signs of an impending eruption, at least in a cosmic time frame, and has for quite some time. From 1838 to 1858, the star called Eta Carinae brightened to rival the light of Sirius, the brightest star in the sky, and then faded to a dim star. Since 1940 it has been brightening again, and scientists think Eta Carinae will detonate in 10,000 to 20,000 years.
Fortunately, Eta Carinae is far away, at least 7,500 light-years from Earth. If it explodes, most of its energy will be scattered or absorbed in the vast emptiness of space. It also happens to be tilted about 45 degrees from the line of sight to Earth, so any type of gamma-ray burst, a high-energy outburst expected with this star's eventual eruption, would miss the Earth. Cosmic rays would be diffused by magnetic fields, and most of the damaging light would not affect life on Earth.
In general, threats to life on Earth from supernovae are extremely small, for all except the nearest explosions those 30 light-years away or closer.
But what if a supernova were 100 times brighter than usual? Would there be any risk to life on Earth then?
Astronomers found such a record-breaking supernova last year, SN 2006gy.

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Blobrana · L

Title: The periodicity of the eta Carinae events
Authors: A. Damineli (1), M. F. Corcoran (3 and 4), D. J. Hillier (2), O. Stahl (5), R. S. Levenhagen (1), N. V. Leister (1), J. H. Groh (1), M. Teodoro (1), J. F. Albacete Colombo (6), F. Gonzalez (7), J. Arias (8), H. Levato (7), M. Grosso (7), N. Morrell (9), R. Gamen (7), G. Wallerstein (10), V. Niemela (11) ((1) Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Brazil (2) Department of Physics and Astronomy, University of Pittsburgh, USA (3) CRESST and X-ray Astrophysics Laboratory, NASA/GSFC, USA (4) Universities Space Research Association, USA (5) ZAH, Landessternwarte, Germany (6) Facultad de Ciencias Astronomicas y Geofisicas de La Plata (FCAGLP) (7) Complejo Astronomico El Leoncito, Argentina (8) Departamento de Física, Universidad de La Serena, Chile (9) Las Campanas Observatory, Carnegie Observatories, Chile (10) Department of Astronomy, University of Washington, USA (11) In memoriam)

Extensive spectral observations of eta Carinae over the last cycle, and particularly around the 2003.5 low excitation event, have been obtained. The variability of both narrow and broad lines, when combined with data taken from two earlier cycles, reveal a common and well defined period. We have combined the cycle lengths derived from the many lines in the optical spectrum with those from broad-band X-rays, optical and near-infrared observations, and obtained a period length of 2022.7±1.3 d.
Spectroscopic data collected during the last 60 years yield an average period of 2020±4 d, consistent with the present day period. The period cannot have changed by more than \Delta P/P=0.0007 since 1948. This confirms the previous claims of a true, stable periodicity, and gives strong support to the binary scenario. We have used the disappearance of the narrow component of HeI 6678 to define the epoch of the Cycle 11 minimum, T_0=JD 2,452,819.8. The next event is predicted to occur on 2009 January 11 (±2 days). The dates for the start of the minimum in other spectral features and broad-bands is very close to this date, and have well determined time delays from the HeI epoch.

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